SOMATOSENSORY INFLUENCES ON RENAL SYMPATHETIC-NERVE ACTIVITY IN ANESTHETIZED WISTAR AND HYPERTENSIVE RATS

This study compared the cardiovascular and renal nerve activity respon ses to somatosensory stimulation with capsaicin in normotensive and hy pertensive rats. The importance of the cardiopulmonary receptors in th ese two states was examined with the use of phenylbiguanide (PBG) infu sion. Subcutaneous capsaicin increased blood pressure (BP), heart rate (HR), and renal nerve activity (RNA) 6-35% (P < 0.01), and total powe r (TP) and %power at HR (%PHR) rose two- to threefold (P < 0.001). PBG reduced basal RNA, TP, and %PHR (20-70%, P < 0.05). PEG did not chang e the cardiovascular, but attenuated the TP and %PHR increases due to capsaicin (P < 0.001-0.01). PBG given to vagotomized normotensive rats normalized the cardiovascular and RNA responses to capsaicin. In hype rtensive rats, capsaicin increased BP, HR, RNA (10-20%), TP, and %PHR (50-70%, P < 0.001). PBG infusion into hypertensive rats decreased RNA (20%, P < 0.01) and the capsaicin-dependent rise in RNA was smaller ( P < 0.05). TP and %PHR were unchanged, except in vagotomized hypertens ive rats given PBG, in which these responses were minimally affected. Somatosensory modulation of RNA power spectra was suppressed by the ca rdiopulmonary receptors in normotensive rats, but in hypertensive rats their impact was much smaller.